In my experience using songs for children of 10 years old it doesn´t work, they are pitiful, just some of them sing, so I agree.
The second statement, i totally agree because we review the previous class so if some of them don't remember something we remember together, the best is at the end, the game. They enjoy playing .
The third statement i agree, there are few ss that work as quikly as they can, because their level is so low ,my class lasts 50 minutes so when somebody ends all the activities helps me to pick up the notebooks and books while i´m cheking the others. So I change intead of an extra activity ss are my helpers to speed it up.